Such vibration isolation systems are known. For example, patent document DE 698 177 50 T2 discloses a vibration isolation system which is used for vibration-isolated mounting of a lithography device.
There, pneumatic springs can be driven via a servo valve and be integrated into the control loop of an active vibration isolation system.
A mass to be isolated is supported on three or more vibration isolators. Vibration isolation from the ground is achieved already above the natural frequency of the spring-mass system by using isolators having a pneumatic spring.
In addition to an active vibration isolation by the pneumatic springs themselves, there are also non-contact actuators such as magnetic actuators, which enable an active vibration isolation, in particular by contributing to a vibration isolation at a higher frequency range.
Additionally, pneumatic springs are used for level adjustment of the system in that case. Therefore, a change in the weight resting on the vibration isolation system leads to a change of the required air pressure, which is only possible within limits and which in many cases leads to an undesired change in the natural frequency.
When using a pneumatic spring, it is problematic to provide a vibration isolation system that allows for level compensation and for which at the same time the vertical and horizontal rigidity is so high that even a natural frequency of more than 5 Hz can be realized in order to achieve short control settling times. In known systems this is not possible or only possible with great effort.